Methods of forming fins for FinFET semiconductor devices and selectively removing some of the fins by performing a cyclical fin cutting process

ABSTRACT

One illustrative method disclosed herein includes forming a plurality of initial fins in a substrate, wherein at least one of the initial fins is a to-be-removed fin, forming a material adjacent the initial fins, forming a fin removal masking layer above the plurality of initial fins, removing a desired portion of the at least one to-be-removed fin by: (a) performing a recess etching process on the material to remove a portion, but not all, of the material positioned adjacent the sidewalls of the at least one to-be-removed fin, (b) after performing the recess etching process, performing a fin recess etching process to remove a portion, but not all, of the at least one to be removed fin and (c) repeating steps (a) and (b) until the desired amount of the at least one to-be-removed fin is removed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Generally, the present disclosure relates to the manufacturing ofsemiconductor devices, and, more specifically, to various methods offorming fins for FinFET semiconductor devices and selectively removingsome of the fins by performing a cyclical fin cutting process.

2. Description of the Related Art

In modern integrated circuits, such as microprocessors, storage devicesand the like, a very large number of circuit elements, especiallytransistors, are provided and operated on a restricted chip area.Immense progress has been made over recent decades with respect toincreased performance and reduced feature sizes of circuit elements,such as transistors. However, the ongoing demand for enhancedfunctionality of electronic devices forces semiconductor manufacturersto steadily reduce the dimensions of the circuit elements and toincrease the operating speed of the circuit elements. The continuingscaling of feature sizes, however, involves great efforts in redesigningprocess techniques and developing new process strategies and tools so asto comply with new design rules. Generally, in complex circuitryincluding complex logic portions, MOS technology is presently apreferred manufacturing technique in view of device performance and/orpower consumption and/or cost efficiency. In integrated circuitsincluding logic portions fabricated by MOS technology, field effecttransistors (FETs) are provided that are typically operated in aswitched mode, that is, these devices exhibit a highly conductive state(on-state) and a high impedance state (off-state). The state of thefield effect transistor is controlled by a gate electrode, whichcontrols, upon application of an appropriate control voltage, theconductivity of a channel region formed between a drain region and asource region.

To improve the operating speed of FETs, and to increase the density ofFETs on an integrated circuit device, device designers have greatlyreduced the physical size of FETs over the years. More specifically, thechannel length of FETs has been significantly decreased, which hasresulted in improving the switching speed of FETs. However, decreasingthe channel length of a FET also decreases the distance between thesource region and the drain region. In some cases, this decrease in theseparation between the source and the drain makes it difficult toefficiently inhibit the electrical potential of the source region andthe channel from being adversely affected by the electrical potential ofthe drain. This is sometimes referred to as a so-called short channeleffect, wherein the characteristic of the FET as an active switch isdegraded.

In contrast to a FET, which has a planar structure, a so-called FinFETdevice has a three-dimensional (3D) structure. FIG. 1A is a perspectiveview of an illustrative prior art FinFET semiconductor device “A” thatis formed above a semiconductor substrate B that will be referenced soas to explain, at a very high level, some basic features of a FinFETdevice. In this example, the FinFET device A includes three illustrativefins C, a gate structure D, sidewall spacers E and a gate cap layer F.Trenches T are formed in the substrate B to define the fins C. The gatestructure D is typically comprised of a layer of gate insulatingmaterial (not separately shown), e.g., a layer of high-k insulatingmaterial (k-value of 10 or greater) or silicon dioxide, and one or moreconductive material layers (e.g., metal and/or polysilicon) that serveas the gate electrode for the device A. The fins C have athree-dimensional configuration: a height H, a width W and an axiallength L. The axial length L corresponds to the direction of currenttravel in the device A when it is operational. The portions of the finsC covered by the gate structure D are the channel regions of the FinFETdevice A. In a conventional process flow, the portions of the fins Cthat are positioned outside of the spacers E, i.e., in the source/drainregions of the device A, may be increased in size or even mergedtogether (a situation not shown in FIG. 1A) by performing one or moreepitaxial growth processes. The process of increasing the size of ormerging the fins C in the source/drain regions of the device A isperformed to reduce the resistance of source/drain regions and/or makeit easier to establish electrical contact to the source/drain regions.Even if an epi “merger” process is not performed, an epi growth processwill typically be performed on the fins C to increase their physicalsize.

In the FinFET device, the gate structure D may enclose both the sidesand the upper surface of all or a portion of the fins C to form atri-gate structure so as to use a channel having a three-dimensionalstructure instead of a planar structure. In some cases, an insulatingcap layer (not shown), e.g., silicon nitride, is positioned at the topof the fins C and the FinFET device only has a dual-gate structure(sidewalls only). Unlike a planar FET, in a FinFET device, a channel isformed perpendicular to a surface of the semiconducting substrate so asto reduce the physical size of the semiconductor device. Also, in aFinFET, the junction capacitance at the drain region of the device isgreatly reduced, which tends to significantly reduce short channeleffects. When an appropriate voltage is applied to the gate electrode ofa FinFET device, the surfaces (and the inner portion near the surface)of the fins C, i.e., the vertically oriented sidewalls and the top uppersurface of the fin, form a surface inversion layer or a volume inversionlayer that contributes to current conduction. In a FinFET device, the“channel-width” is estimated to be about two times (2×) the verticalfin-height plus the width of the top surface of the fin, i.e., the finwidth. Multiple fins can be formed in the same foot-print as that of aplanar transistor device. Accordingly, for a given plot space (orfoot-print), FinFETs tend to be able to generate significantly higherdrive current density than planar transistor devices. Additionally, theleakage current of FinFET devices after the device is turned “OFF” issignificantly reduced as compared to the leakage current of planar FETs,due to the superior gate electrostatic control of the “fin” channel onFinFET devices. In short, the 3D structure of a FinFET device is asuperior MOSFET structure as compared to that of a planar FET,especially in the 20 nm CMOS technology node and beyond. The gatestructures D for such FinFET devices may be manufactured using so-called“gate-first” or “replacement gate” (gate-last) manufacturing techniques.

Both FET and FinFET semiconductor devices have an isolation structure,e.g., a shallow trench isolation structure that is formed in thesemiconducting substrate around the device so as to electrically isolatethe semiconductor device. Traditionally, isolation structures werealways the first structure that was formed when manufacturingsemiconductor devices. The isolation structures were formed by etchingthe trenches for the isolation structures and thereafter filling thetrenches with the desired insulating material, e.g., silicon dioxide.After the isolation structures were formed, various process operationswere performed to manufacture the semiconductor device. In the case of aFinFET device, this involved masking the previously formed isolationstructure and etching the trenches in the substrate that defined thefins. As FinFET devices have been scaled to meet ever increasingperformance and size requirements, the width W of the fins C has becomevery small, e.g., 6-12 nm, and the fin pitch has also been significantlydecreased, e.g., the fin pitch may be on the order of about 30-60 nm.

However, as the dimensions of the fins became smaller, problems arosewith manufacturing the isolation structures before the fins were formed.As one example, trying to accurately define very small fins in regionsthat were separated by relatively large isolation regions was difficultdue to the non-uniform spacing between various structures on thesubstrate. One manufacturing technique that is employed in manufacturingFinFET devices is to initially form the trenches T in the substrate B todefine multiple “fins” that extend across the substrate, and thereafterremove some of the fins C where larger isolation structures will beformed. Using this type of manufacturing approach, better accuracy andrepeatability may be achieved in forming the fins C to very smalldimensions due to the more uniform environment in which the etchingprocess that forms the trenches T is performed.

After the trenches T have been formed, some of the fins C must beremoved to create room for or define the spaces where isolation regionswill ultimately be formed. There are two commonly employed techniquesfor accomplishing the goal of removing the desired number of fins C. Onesuch removal process is typically referred to as “Fins-cut-First,” aswill be described with reference to FIGS. 1B-1F. Accordingly, FIG. 1Bdepicts the device 10 after a patterned hard mask layer 14, e.g., apatterned layer of silicon nitride, was formed above the substrate 12 inaccordance with the desired fin pattern and pitch. In the depictedexample, only a single fin will be removed, i.e., the fin 15corresponding to the feature 14A, to make room for the isolation region.However, as will be recognized by those skilled in the art, dependingupon the desired final size of the isolation region, more than one finmay be removed.

FIG. 1C depicts the device 10 after a patterned masking layer 16, e.g.,a patterned layer of photoresist, has been formed above the patternedhard mask layer 14. The patterned masking layer 16 has an opening thatexposes the feature 14A for removal.

FIG. 1D depicts the device 10 after an etching process has beenperformed through the patterned masking layer 16 so as to remove theexposed feature 14A of the patterned hard mask layer 14.

FIG. 1E depicts the device 10 after the patterned masking layer 16 wasremoved and after an anisotropic etching process was performed throughthe patterned hard mask layer 14 (without the feature 14A) so as todefine full-depth trenches 17 in the substrate 12 that define the fins15. Due to the removal of the feature 14A, this etching process removesthe portions of the substrate 12 that would have otherwise formed a fin15 in the area under the feature 14A. One problem with the“fin-cut-first” approach is that it inevitably causes different finsizes, i.e., the dimensions 15X and 15Y are different. This isespecially true between fins 15 inside an array of fins and the fins atthe edge of the active region that is close to the isolation region.This occurs due to etch loading effects wherein there are different etchrates and etch profiles due to differing patterning densities, pitch,etc.

FIG. 1F depicts the device 10 after several process operations wereperformed. First, a layer of insulating material 18, such as silicondioxide, was formed so as to overfill the trenches 17. A chemicalmechanical polishing (CMP) process was then performed to planarize theupper surface of the insulating material 18 with the top of thepatterned hard mask 14. Thereafter, an etch-back process was performedto recess the layer of insulating material 18 between the fins 15 andthereby expose the upper portions of the fins 15, which corresponds tothe final fin height of the fins 15. At this point in the process, thepatterned hard mask 14 may or may not be thereafter removed. Next, thegate structure of the device 10 may be formed using either gate-first orgate-last manufacturing techniques.

Another fin removal process is typically referred to as “Fins-cut-Last,”as will be described with reference to FIGS. 1G-1L. FIG. 1G depicts thedevice 10 after the patterned hard mask layer 14 was formed above thesubstrate 12 in accordance with the desired fin pattern and pitch. Asbefore, in the depicted example, only a single fin will be removed,i.e., the fin 15 corresponding to the feature 14A, to make room for theisolation region. However, as will be recognized by those skilled in theart, depending upon the desired final size of the isolation region, morethan one fin may be removed.

FIG. 1H depicts the device 10 after an anisotropic etching process wasperformed through the patterned hard mask layer 14 so as to definefull-depth trenches 17 in the substrate 12 that define the fins 15. Notethat, in the Fins-cut-Last approach, the size of the fins is veryuniform up near the top of the initial fins 15, i.e., the dimension 15Ais approximately equal to the dimension 15B. This is primarily due tothe fact that, in this approach, fins 15 are formed everywhere on thewafer and there is no undesirable etch loading effects.

FIGS. 1I-1K depict the device 10 after several process operations wereperformed. First, a layer of insulating material 19, such as silicondioxide, was formed so as to overfill the trenches 17. Then a CMPprocess was performed to planarize the upper surface of the layer ofinsulating material 19 with the patterned hard mask layer 14. Next, apatterned masking layer 22, e.g., a patterned layer of photoresist, wasformed above the layer of insulating material 19. The patterned hardmask layer 22 has an opening 22A positioned above the portion of theunderlying fin that is to be removed. FIG. 1J is a plan view of thepatterned masking layer 22 with a generally rectangular-shaped opening22A positioned above the portion of the underlying fin that is to beremoved.

FIG. 1K depicts the device 10 after one or more anisotropic etchingprocesses were performed to remove the exposed portions of the layer ofinsulating material 19, the exposed portions of the hard mask layer 14,i.e., the feature 14A, and the underlying fin 15. This results in theformation of a trench 24 in the layer of insulating material 19.Typically, as shown in the plan view in FIG. 1J the trench 24 will takethe form of a rectangle that corresponds approximately to the opening22A in the patterned hard mask layer 22. Inevitably, there will be someinward tapering of the sidewalls of the trench 24. Although not depictedin the drawings, after the trench 24 is formed, the patterned maskinglayer 22 will be removed and additional oxide material (not shown) willbe formed through the opening 22A in the trench 24 where the fin 15 wasremoved. Then a chemical mechanical polishing (CMP) process will beperformed to planarize the upper surface of all of the insulatingmaterials with the top of the patterned hard mask 14. Thereafter, theisolation regions between devices will be masked and an etch-backprocess will be performed to recess the layer of insulating material 19between the fins 15 for each device and thereby expose the upperportions of the fins 15, which corresponds to the final fin height ofthe fins 15.

One problem with the fins-cut-last approach is that if the criticaldimension (CD) 24X of the opening 22A of the trench 24 is relativelylarge, then there is less margin for misalignment error when removingthe unwanted fin, i.e., there is less margin for error so as to avoiddamaging the adjacent fins when the trench 24 is etched. With referenceto FIG. 1L, if the CD 24X of the opening 22A is kept small, there willtypically be some residual portion 15X of the fin 15 remaining at thebottom of the trench 24. If the size of the opening 22A is increased inan effort to insure complete removal of the unwanted residual finmaterials 15X at the bottom of the trench 24, then there is a muchgreater likelihood of damaging the fins adjacent the trench 24 when itis etched. These issues only get worse as the depth of the trench 24increases and as packing densities increase.

Some of the aforementioned problems could potentially be remedied byperforming a selective isotropic etching process to limit or eliminatethe residual fin material 15X relative to the surrounding insulatingmaterial 19. In one sense, removing the unwanted residual fin material15X by performing such an isotropic etching process would be beneficialas compared to removing the fins by performing an anisotropic etchingprocess because, due to the selective and isotropic nature of theprocess, there would be less chance of damaging adjacent fins (if the CD24X is too large) and less chance of leaving the undesirable residualfin material 15X at or near the bottom of the trench 24 (if the CD 24Xis too small). However, with referenced to FIG. 1J, performing such anisotropic etching process may cause unwanted loss of the remainingportions of the fin 15 positioned below the edges of the rectangularopening 22A (when viewed from above) in the patterned masking layer 22.That is, due to the nature of an isotropic etching process, there may besome undesirable loss of the fin material in the directions indicated bythe arrows 21 in FIG. 1J.

The present disclosure is directed to various methods of forming finsfor FinFET semiconductor devices and selectively removing some of thefins by performing a cyclical fin cutting process that may solve orreduce one or more of the problems identified above.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an exhaustive overview of the invention. It is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts in a simplified form as a prelude to the more detaileddescription that is discussed later.

Generally, the present disclosure is directed to various methods offorming fins for FinFET semiconductor devices and selectively removingsome of the fins by performing a cyclical fin cutting process. Oneillustrative method disclosed herein includes, among other things,forming a plurality of trenches in a semiconductor substrate to therebydefine a plurality of initial fins in the substrate, the initial finshaving sidewalls, wherein at least one of the initial fins is ato-be-removed fin, forming a material (e.g., liner layer or a layer ofinsulating material) adjacent at least the sidewalls of the initial finsand within the trenches, forming a fin removal masking layer above theplurality of initial fins, the fin removal masking layer having anopening positioned above the at least one to-be-removed fin and at leasta portion of the material that was formed adjacent the at least oneto-be-removed fin, removing a desired portion of the at least oneto-be-removed fin by, (a) performing a recess etching process on thematerial that was formed adjacent the at least one to-be-removed fin toremove a portion, but not all, of the material that was formed adjacentthe at least one to-be-removed fin, (b) after performing the recessetching process, performing a fin recess etching process to remove aportion, but not all, of the at least one to-be-removed fin, and (c)repeating steps (a) and (b) until the desired amount of the at least oneto-be-removed fin is removed and forming an insulating material in anarea that includes an area formerly occupied by the at least oneto-be-removed fin.

In another embodiment, a method disclosed herein includes forming aplurality of trenches in a semiconductor substrate to thereby define aplurality of initial fins in the substrate, wherein at least one of theinitial fins is a to-be-removed fin, forming a liner layer adjacent atleast the sidewalls of the initial fins, forming a layer of insulatingmaterial adjacent the liner layer and within the trenches, forming a finremoval masking layer above the plurality of initial fins, the finremoval masking layer having an opening positioned above the at leastone to-be-removed fin and the liner layer positioned adjacent the atleast one to-be-removed fin, removing a desired portion of the at leastone to-be-removed fin by: (a) performing a liner recess etching processon the liner layer to remove a portion, but not all, of the liner layerpositioned adjacent the sidewalls of the at least one to-be-removed fin,(b) after performing the liner recess etching process, performing a finrecess etching process to remove a portion, but not all, of the at leastone to be removed fin, and (c) repeating steps (a) and (b) until thedesired amount of the at least one to-be-removed fin is removed andforming an insulating material in an area that includes an area formerlyoccupied by the at least one to-be-removed fin.

Another illustrative method includes, among other things, forming atrench patterning hard mask layer above a surface of a semiconductorsubstrate, performing at least one first etching process through thetrench patterning hard mask layer to define a plurality of trenches in asemiconductor substrate to thereby define a plurality of initial fins inthe substrate, wherein at least one of the initial fins is ato-be-removed fin, forming a layer of insulating material within thetrenches, forming a patterned fin removal masking layer above theplurality of initial fins and the layer of insulating material, thepatterned fin removal masking layer having an opening positioned abovethe at least one to-be-removed fin, wherein a portion of the trenchpatterning hard mask layer is positioned above the at least oneto-be-removed fin and below the opening in the patterned fin removalmasking layer, performing at least one second etching process throughthe opening in the patterned fin removal masking layer to remove atleast the underlying portion of the trench patterning hard mask layer,after performing said at least one second etching process, performing athird etching process through the opening in the patterned fin removalmasking layer to define a fin opening in the layer of insulatingmaterial that exposes substantially all of a vertical height of the atleast one to-be-removed fin, performing a fourth etching process throughthe opening in the patterned fin removal masking layer and the finopening in the layer of insulating material until the desired amount ofthe at least one to-be-removed fin is removed and forming an insulatingmaterial in an area that includes an area formerly occupied by the atleast one to-be-removed fin.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1A is a perspective view of one illustrative embodiment of a priorart FinFET device;

FIGS. 1B-1L depict illustrative prior art methods of removing selectedfin structures when forming FinFET semiconductor devices;

FIGS. 2A-2N depict various illustrative methods disclosed herein forforming fins for FinFET semiconductor devices and selectively removingsome of the fins by performing a cyclical fin cutting process; and

FIGS. 3A-3N depict other illustrative methods disclosed herein forforming fins for FinFET semiconductor devices and selectively removingsome of the fins by performing a unique process flow and a cyclicaletching process sequence.

While the subject matter disclosed herein is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Various illustrative embodiments of the invention are described below.In the interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present subject matter will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present disclosure with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present disclosure. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase.

The present disclosure is directed to various methods of forming finsfor FinFET semiconductor devices and selectively removing some of thefins by performing a cyclical fin cutting process. As will be readilyapparent to those skilled in the art upon a complete reading of thepresent application, the methods disclosed herein may be employed inmanufacturing a variety of different devices, including, but not limitedto, logic devices, memory devices, etc. With reference to the attachedfigures, various illustrative embodiments of the methods and devicesdisclosed herein will now be described in more detail.

FIGS. 2A-2N depict one illustrative embodiment of a method disclosedherein of forming fins on a FinFET semiconductor device 100 that isformed on a bulk semiconducting substrate 102. FIG. 2A is a simplifiedview of an illustrative FinFET semiconductor device 100 at an earlystage of manufacturing. As will be recognized by those skilled in theart after a complete reading of the present application, theillustrative FinFET device 100 described herein may be either an N-typeFinFET device or a P-type FinFET device. In this illustrativeembodiment, the substrate 102 has a bulk semiconducting materialconfiguration. The substrate 102 may be made of silicon or it may bemade of materials other than silicon. Thus, the terms “substrate” or“semiconducting substrate” should be understood to cover all forms ofall semiconductor materials.

FIG. 2A depicts the device 100 after a trench patterning masking layer104, e.g., a trench patterning hard mask layer, has been formed abovethe substrate 102 that corresponds to the desired pattern of fins to beformed in the substrate 102. The trench patterning masking layer 104 isintended to be representative in nature as it may be comprised of avariety of materials, such as, for example, a photoresist material,silicon nitride, silicon oxynitride, etc. Moreover, the trenchpatterning masking layer 104 may be comprised of multiple layers ofmaterial, such as, for example, a silicon nitride layer and a layer ofsilicon dioxide. The trench patterning masking layer 104 may be formedby depositing the layer(s) of material that comprise the trenchpatterning masking layer 104 and thereafter directly patterning themasking layer 104 using known photolithography and etching techniques.Alternatively, the trench patterning masking layer 104 may be formed byusing known sidewall image transfer techniques. Thus, the particularform and composition of the trench patterning masking layer 104 and themanner in which it is made should not be considered a limitation of thepresent invention. In the case where the trench patterning masking layer104 is comprised of one or more hard mask layers, such layers may beformed by performing a variety of known processing techniques, such as achemical vapor deposition (CVD) process, an atomic layer deposition(ALD) process, an epitaxial deposition process (EPI), or plasma enhancedversions of such processes, and the thickness of such a layer(s) mayvary depending upon the particular application.

FIG. 2B depicts the device 100 after a first etching process 106 wasperformed through the trench patterning masking layer 104 to define aplurality of trenches 106X in the substrate 102. The trenches 106Xdefine a plurality of initial fins 107 having a fin height 107H. Due tothe fact that the fins 107 are formed across the substrate, there islittle or no undesirable variation in the width (CD) of the initial fins107 since there is no adverse etch loading effects, as discussed in thebackground section of this application. The magnitude of the fin height107H may vary depending upon the particular device under construction,e.g., 100-200 nm. In the depicted example herein, the middle fin 107R ofthe plurality of initial fins 107 is a to-be-removed fin that will beremoved using the process flow disclosed below. Of course, as will beappreciated by those skilled in the art after a complete reading of thepresent application, any desired number of fins can be removed using themethods disclosed herein.

In the illustrative example depicted in the attached figures, thetrenches 106X and the initial fins 107 are all of a uniform size andshape. However, such uniformity in the size and shape of the trenches106X and the initial fins 107 is not required to practice at least someaspects of the inventions disclosed herein. In the example depictedherein, the trenches 106X are depicted as having been formed byperforming a plurality of anisotropic etching processes. In some cases,the trenches 106X may have a reentrant profile near the bottom of thetrenches 106X. To the extent the trenches 106X are formed by performinga wet etching process, the trenches 106X may tend to have a more roundedconfiguration or non-linear configuration as compared to the generallylinear configuration of the trenches 106X that are formed by performingan anisotropic etching process. In other cases, the trenches 106X may beformed in such a manner that the initial fins 107 have a taperedcross-sectional configuration (wider at the bottom than at the top atthis point in the process flow). Thus, the size and configuration of thetrenches 106X, and the manner in which they are made, should not beconsidered a limitation of the present invention.

FIG. 2C depicts the device 100 after a liner layer 109 was formedadjacent the sidewalls of fins 107 and above the trench patterning hardmask 104. In some embodiments, prior to forming the liner layer 109, athin layer of silicon dioxide (not shown) may be formed on the sidewallsof the fins 107. The liner layer 109 may be comprised of a variety ofdifferent materials, it may be formed to any desired thickness and itmay be formed using any of a variety of process operations. In oneillustrative embodiment, the liner layer 109 may be comprised of amaterial that exhibits good etch selectivity relative to the material ofthe fins 107. For example, in one illustrative embodiment, the linerlayer 109 may be comprised of silicon nitride, it may be formed to athickness of about 3-6 nm, and it may be formed by performing aconformal ALD or CVD process.

FIG. 2D depicts the device 100 after several process operations wereperformed. First, a layer of insulating material 110, such as silicondioxide, was formed so as to overfill the trenches 106X. A chemicalmechanical polishing (CMP) process was then performed to planarize theupper surface of the insulating material 110 with the top of the linerlayer 109, i.e., to define a common planarized surface.

FIG. 2E depicts the device 100 after a patterned fin removal (fin-cut)hard mask layer 112 was formed above the device 100. The patterned finremoval hard mask layer 112 has an opening 112A that is positioned abovethe to-be-removed fin—the fin 107R. The patterned fin removal hard masklayer 112 may be formed by depositing a layer of appropriate material,e.g., silicon dioxide, and it may be patterned by forming a patternedlayer of photoresist material (not shown) and by performing atraditional etching process. The patterned fin removal hard mask layer112 may be formed to any desired thickness.

FIG. 2F depicts the device after one or more timed, first liner layeretching processes was performed through the opening 112A in thepatterned fin removal hard mask layer 112 to remove underlying portions,but not all, of the liner layer 109 and the underlying portion of thetrench patterning hard mask 104 selectively relative to the layer ofinsulating material 110 and the to-be-removed fin 107R. This processoperation exposes an upper surface 107U of the to-be-removed fin 107R,and recesses the liner layer 109 such that the liner layer 109 exposedunder the opening 112A has a first recessed upper surface 109R1 that ispositioned below the upper surface 107U of the fin 107R by a distanceof, for example, 1-5 nm. This recessing exposes a portion, but not all,of the vertical sidewalls of the to-be-removed fin 107R.

FIG. 2G depicts the device 100 after one or more timed, second finetching processes were performed through the opening 112A in thepatterned fin removal hard mask layer 112 to remove portions of theto-be-removed fin 107R selectively relative to the layer of insulatingmaterial 110 and the liner layer 109. This process operation consumessome, but not all, of the to-be-removed fin 107R. This second finetching process removes a portion of the to-be-removed fin 107R suchthat it has a first recessed upper surface 107R1 that is positionedbelow the first recessed upper surface 109R1 of the liner layer 109 by adistance of, for example, 10-20 nm.

As will be described more fully below, the cyclical etching sequencedescribed above, i.e., the first liner etch process and second finetching process, are repeated until the desired amount or all of theto-be-removed fin 107R is removed. The amount of the fin 107R removedduring each fin etching process may vary depending upon the particularapplication. In one illustrative example, approximately 10-30 nm(height) of the vertical height of the to-be-removed fin 107R may beremoved in each of the above-described second etching processes. Thus,in the example where the fins 107 have an initial height 107H of about100 nm, 3-4 of the fin etching processes described above may beperformed to remove the desired amount of the to-be-removed fin 107R. Ofcourse, the number of cycles performed may vary depending upon theparticular application

FIG. 2H-2I depict the device 100 after another of the dual-etch etchingprocess discussed above has been performed on the device. Morespecifically, FIG. 2H depicts the device 100 after another liner layeretching process was performed to remove additional portions, but notall, of the liner layer 109 selectively relative to the layer ofinsulating material 110 and the to-be-removed fin 107R. The etchingprocess performed in FIG. 2H further recesses the liner layer 109 suchthat the liner layer 109 has a second recessed upper surface 109R2 thatis positioned below the first recessed upper surface 107R1 of theto-be-removed fin 107R. FIG. 2I depicts the device 100 after another ofthe fin etching processes was performed to remove additional portions ofthe to-be-removed fin 107R selectively relative to the layer ofinsulating material 110 and the liner layer 109. This process operationremoves an additional amount, but not all, of the remaining portion ofthe fin 107R. This additional fin etching process removes a portion ofthe to-be-removed fin 107R such that it has a second recessed uppersurface 107R2 that is positioned below the second recessed upper surface109R2 of the liner layer 109.

FIGS. 2J-2K depict the device 100 after another of the dual-etch etchingprocess discussed above has been performed on the device. Morespecifically, FIG. 2J depicts the device 100 after another liner layeretching process (the third in the depicted example) was performed toremove additional portions of the liner layer 109 selectively relativeto the layer of insulating material 110 and the to-be-removed fin 107R.This third liner etching process further recesses the liner layer 109such that the liner layer 109 has a third recessed upper surface 109R3that is positioned below the second recessed upper surface 107R2 of thefin 107R. FIG. 2K depicts the device 100 after another of the finetching processes was performed to remove additional portions of theto-be-removed fin 107R selectively relative to the layer of insulatingmaterial 110 and the liner layer 109. This process operation removes anadditional amount, but not all, of the remaining portion of theto-be-removed fin 107R. This additional fin etching process removes aportion of the fin 107R such that it has a third recessed upper surface107R3 that is positioned below the third recessed upper surface 109R3 ofthe liner layer 109.

FIG. 2L depicts the device 100 after the desired number of the lineretch and fin etch process cycles have been performed such theto-be-removed fin 107R has been removed and has a final removed uppersurface 107F and the liner layer 109 was recessed to its final recessedupper surface 109F. In the depicted example, the final surface 107F ofthe removed fin is depicted as being positioned above the bottom of thetrench 106X. Of course, if desired the processing sequences disclosedherein may be performed such that the recessed surface 107F ispositioned at a level that is below the level of the bottom of thetrenches 106X.

FIG. 2M depicts the device 100 after several process operations wereperformed. First, a layer of insulating material 114, such as silicondioxide, was formed so as to overfill the opening left by removal of thefin 107R. A chemical mechanical polishing (CMP) process was thenperformed to planarize the upper surface of the insulating material 114with the top of the liner layer 109.

FIG. 2N depicts the device 100 after several additional processoperations were performed. First, an etch-back process was performed torecess the layers of insulating material 110, 114 to the desired levelbetween the remaining fins 107 and thereby expose a desired amount 107Yof the initial fins 107, which corresponds to the final fin height forthe fins of the device 100. Then, another recess etching process wasperformed to remove the remaining portions of the trench patterning hardmask 104 and portions of the liner layer 109. At the point offabrication depicted in FIG. 2N, traditional manufacturing operationsmay be performed to complete the formation of the product 100. Forexample, a gate structure (not shown) of the device 100 may be formedusing either gate-first or gate-last manufacturing techniques, varioussource/drain and gate contact structures may be formed on the device,various metallization layers may be formed above the product 100 usingknown processing techniques, etc.

FIGS. 3A-3N depict other illustrative methods disclosed herein forforming fins for FinFET semiconductor devices and selectively removingsome of the fins by performing a unique process flow and a cyclicaletching process sequence. FIG. 3A depicts the device 100 at the point inprocessing that corresponds to that depicted in FIG. 2B, i.e., after thetrenches 106X were formed in the substrate to define the initial fins107.

FIG. 3B depicts the device 100 after several process operations wereperformed. First, the above-described layer of insulating material 110,such as silicon dioxide, was formed so as to overfill the trenches 106X.A chemical mechanical polishing (CMP) process was then performed toplanarize the upper surface of the insulating material 110 with the topof the trench patterning hard mask layer 104.

FIG. 3C depicts the device 100 after a fin removal hard mask layer 120,e.g., silicon nitride, was formed above the device 100 and a patternedlayer of photoresist material 122 was formed above the device usingtraditional photolithography tools and techniques. The fin removal hardmask layer 120 may be formed to any desired thickness.

FIG. 3D depicts the device 100 after one or more etching processes wereperformed through the patterned photoresist layer 122 so as to patternthe fin removal hard mask layer 120 and remove portions of the trenchpatterning hard mask layer 104 and the layer of insulating material 110underlying the opening 120A in the patterned fin removal hard mask layer120. This process operation exposes an upper surface 107U of theto-be-removed fin 107R.

FIG. 3E depicts the device 100 after the patterned layer of photoresistmaterial 122 was removed and after an anisotropic etching process wasperformed through the opening 120A in the patterned fin removal hardmask layer 120 on the layer of insulating material 110 to define anopening 110X that may expose a substantial portion of the overall heightand sidewalls of the to-be-removed fin 107R.

FIG. 3F depicts the device 100 after an anisotropic etching process wasperformed through the patterned fin removal hard mask layer 120 toremove the desired amount, and in some cases substantially all, of theto-be-removed fin 107R selectively relative to the layer of insulatingmaterial 110. In the depicted example, a sufficient amount of the fin107R is removed such that the surface 107S is positioned at a level thatis below the level of the bottom of the trenches 106X.

FIG. 3G depicts the device 100 after several process operations wereperformed. First, the above-described layer of insulating material 114,such as silicon dioxide, was formed so as to overfill the opening leftby removal of the fin 107R. Then, one or more CMP processes wereperformed to remove the patterned fin removal hard mask layer 120 and toplanarize the upper surface of the insulating materials 110, 114 withthe top of the trench patterning hard mask 104.

FIG. 3H depicts the device 100 after several additional processoperations were performed. First, an etch-back process was performed torecess the layers of insulating material 110, 114 to the desired levelbetween the remaining fins 107 and thereby expose a desired amount 107Yof the fins 107, which corresponds to the final fin height for the finsof the device 100. Then, another etching process was performed to removethe remaining portions of the trench patterning hard mask 104. At thepoint of fabrication depicted in FIG. 3H, traditional manufacturingoperations may be performed to complete the formation of the product100. For example, a gate structure (not shown) of the device 100 may beformed using either gate-first or gate-last manufacturing techniques,various source/drain and gate contact structures may be formed on thedevice, various metallization layers may be formed above the product 100using known processing techniques, etc.

The manner in which the fin 107R may be removed using the cyclicaletching process described above will now be described with reference toFIGS. 3I-3N. As with the previously described example of using thecyclical etching sequence described above, in this embodiment, a firstetch process will be performed to recess the materials positionedadjacent the fin 107R, which in this example is the insulation material110, and, thereafter, the above-described second fin etching process,are repeated until the desired amount or all of the to-be-removed fin107R is removed.

Starting with the structure depicted in FIG. 3D, FIG. 3I depicts thedevice 100 after several process operations were performed. First, thepatterned photoresist mask 122 was removed. Then, one or more timed,first etching processes were performed through the opening 120A in thepatterned fin removal hard mask layer 120 to remove underlying portions,but not all, of the layer of insulating material 110 selectivelyrelative to the to-be-removed fin 107R. This process operation exposesthe layer of insulating material 110 such that the layer of insulatingmaterial 110 exposed under the opening 120A has a first recessed uppersurface 110R1 that is positioned below the upper surface 107U of the fin107R by a distance of, for example, 5-15 nm. This recessing exposes aportion, but not all, of the vertical sidewalls of the to-be-removed fin107R.

FIG. 3J depicts the device 100 after one or more timed, second finetching processes were performed through the opening 120A in thepatterned fin removal hard mask layer 120 to remove portions of theto-be-removed fin 107R selectively relative to the layer of insulatingmaterial 110. This process operation consumes some, but not all, of theto-be-removed fin 107R. This second fin etching process removes aportion of the to-be-removed fin 107R such that it has a first recessedupper surface 107R1 that is positioned below the first recessed uppersurface 110R1 of the layer of insulating material 110 by a distance of,for example, 1-10 nm.

As will be described more fully below, the cyclical etching sequencedescribed above, i.e., the first etch process (to remove some of thelayer of insulating material 110) and the second fin etching process (toremove portions of the fin 107R), are repeated until the desired amountor all of the to-be-removed fin 107R is removed. As with the case above,the amount of the fin 107R removed during each fin etching process mayvary depending upon the particular application.

FIGS. 3K-3L depict the device 100 after another of the dual-etch etchingprocesses discussed above has been performed on the device. Morespecifically, FIG. 3K depicts the device 100 after another first etchingprocess was performed to remove additional portions, but not all, of thelayer of insulating material 110 selectively relative to theto-be-removed fin 107R. The first etching process performed in FIG. 3Kfurther recesses the layer of insulating material 110 such that thelayer of insulating material 110 has a second recessed upper surface110R2 that is positioned below the first recessed upper surface 107R1 ofthe to-be-removed fin 107R. FIG. 3L depicts the device 100 after anotherof the fin etching processes was performed to remove additional portionsof the to-be-removed fin 107R selectively relative to the layer ofinsulating material 110. This process operation removes an additionalamount, but not all, of the remaining portion of the fin 107R. Thisadditional fin etching process removes a portion of the to-be-removedfin 107R such that it has a second recessed upper surface 107R2 that ispositioned below the second recessed upper surface 110R2 of the layer ofinsulating material 110.

FIG. 3M depicts the device 100 after the desired number of the first andsecond etching process cycles have been performed such that theto-be-removed fin 107R has been removed and has a final removed uppersurface 107F and the layer of insulating material 110 was recessed toits final recessed upper surface 110F. In the depicted example, thefinal surface 107F of the removed fin is depicted as being positionedabove the bottom of the trench 106X. Of course, if desired theprocessing sequences disclosed herein may be performed such that therecessed surface 107F is positioned at a level that is below the levelof the bottom of the trenches 106X.

FIG. 3N depicts the device 100 after the above-described CMP and recessetching processes were performed to expose a desired amount 107Y of theinitial fins 107, which corresponds to the final fin height for the finsof the device 100. At the point of fabrication depicted in FIG. 3N,traditional manufacturing operations may be performed to complete theformation of the product 100. For example, a gate structure (not shown)of the device 100 may be formed using either gate-first or gate-lastmanufacturing techniques, various source/drain and gate contactstructures may be formed on the device, various metallization layers maybe formed above the product 100 using known processing techniques, etc.

As will be appreciated by those skilled in the art after a completereading of the present application, the cyclical fin removal processprovides several advantages relative to the prior art fin removaltechniques discussed in the background section of this application.First, by removing relatively small portions of the vertical height ofthe fin 107R during each of the second etching processes, the etchshadowing effect (wherein the undesirable residual fin material 15X isformed (see FIG. 1L), may be reduced or eliminated when performing theanisotropic fin etching processes. Additionally, using the methodsdisclosed herein, the fin 107R may be removed by performing anisotropicetching processes, thereby avoiding the problems associated withperforming an isotropic etching process to insure complete removal ofthe fin 207R, namely the undercutting of the desired fins in thedirection indicated by the arrows 21 shown in FIG. 1J.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Note that the use of terms, such as “first,” “second,”“third” or “fourth” to describe various processes or structures in thisspecification and in the attached claims is only used as a shorthandreference to such steps/structures and does not necessarily imply thatsuch steps/structures are performed/formed in that ordered sequence. Ofcourse, depending upon the exact claim language, an ordered sequence ofsuch processes may or may not be required. Accordingly, the protectionsought herein is as set forth in the claims below.

What is claimed is:
 1. A method, comprising: forming a plurality of trenches in a semiconductor substrate to thereby define a plurality of initial fins in said substrate, said initial fins having sidewalls, wherein at least one of said initial fins is a to-be-removed fin; forming a material adjacent at least said sidewalls of said initial fins and within said trenches; forming a fin removal masking layer above said plurality of initial fins, said fin removal masking layer having an opening positioned above said at least one to-be-removed fin and at least a portion of said material that was formed adjacent said at least one to-be-removed fin; removing a desired portion of said at least one to-be-removed fin by: a) performing a recess etching process on said material that was formed adjacent said at least one to-be-removed fin to remove a portion, but not all, of said material that was formed adjacent said at least one to-be-removed fin; b) after performing said recess etching process, performing a fin recess etching process to remove a portion, but not all, of said at least one to-be-removed fin; and c) repeating steps (a) and (b) until the desired amount of said at least one to-be-removed fin is removed; and forming an insulating material in an area that includes an area formerly occupied by said at least one to-be-removed fin.
 2. The method of claim 1, wherein said material that was formed adjacent said at least one to-be-removed fin is one of a liner layer or a layer of insulating material that was blanket deposited within said trenches.
 3. The method of claim 1, wherein forming said material adjacent at least said sidewalls of said initial fins and within said trenches comprises performing a conformal deposition process to deposit a liner layer adjacent said sidewalls of said initial fins and above a bottom of said trenches.
 4. The method of claim 1, wherein each of said etching processes set forth in step (b) consumes between 10-30 nm of a vertical height of said at least one to-be-removed fin.
 5. The method of claim 1, wherein, after performing step (a), an upper surface of the recessed material that was formed adjacent said at least one to-be-removed fin is positioned at a level that is below a level of an upper surface of said at least one to-be-removed fin.
 6. The method of claim 1, wherein steps (a) and (b) are repeated at least three times.
 7. A method, comprising: forming a plurality of trenches in a semiconductor substrate to thereby define a plurality of initial fins in said substrate, said initial fins having sidewalls, wherein at least one of said initial fins is a to-be-removed fin; forming a liner layer adjacent at least said sidewalls of said initial fins; forming a layer of insulating material adjacent said liner layer and within said trenches; forming a fin removal masking layer above said plurality of initial fins, said fin removal masking layer having an opening positioned above said at least one to-be-removed fin and said liner layer positioned adjacent said at least one to-be-removed fin; removing a desired portion of said at least one to-be-removed fin by: (a) performing a liner recess etching process on said liner layer to remove a portion, but not all, of said liner layer positioned adjacent said sidewalls of said at least one to-be-removed fin; (b) after performing said liner recess etching process, performing a fin recess etching process to remove a portion, but not all, of said at least one to-be-removed fin; and (c) repeating steps (a) and (b) until the desired amount of said at least one to-be-removed fin is removed; and forming an insulating material in an area that includes an area formerly occupied by said at least one to-be-removed fin.
 8. The method of claim 7, further comprising performing at least one additional recess etching process to recess said layer of insulating material and to recess said liner layer such that a desired final fin height of the remaining plurality of initial fins are exposed above the recessed layer of insulating material and the recessed liner layer.
 9. The method of claim 7, wherein forming said liner layer adjacent said sidewalls of said initial fins comprises performing a conformal deposition process to deposit said liner layer adjacent said sidewalls of said initial fins and above a bottom of said trenches.
 10. The method of claim 7, wherein said liner layer is comprised of silicon nitride.
 11. The method of claim 7, wherein each of said etching processes set forth in step (b) consumes between 10-30 nm of a vertical height of said at least one to-be-removed fin.
 12. The method of claim 7, wherein, after performing step (a), an upper surface of said recessed liner layer is positioned at a level that is below a level of an upper surface of said at least one to-be-removed fin.
 13. The method of claim 7, wherein the etching steps performed in step (b) are anisotropic etching processes.
 14. A method, comprising: forming a trench patterning hard mask layer above a surface of a semiconductor substrate; performing an etching process through said trench patterning hard mask layer to define a plurality of trenches in a semiconductor substrate to thereby define a plurality of initial fins in said substrate, said initial fins having sidewalls, wherein at least one of said initial fins is a to-be-removed fin; forming a liner layer adjacent at least said sidewalls of said initial fins and above said trench patterning hard mask layer; forming a layer of insulating material on said liner layer and within said trenches; forming a fin removal masking layer above said plurality of initial fins, said fin removal masking layer having an opening positioned above said at least one to-be-removed fin, said liner layer positioned adjacent said at least one to-be-removed fin and a portion of said trench patterning hard mask layer positioned above said at least one to-be-removed fin; removing a desired portion of said at least one to-be-removed fin by: a) performing a liner recess etching process on said liner layer to remove the portion of said trench patterning hard mask layer and a portion, but not all, of said liner layer positioned adjacent said sidewalls of said at least one to-be-removed fin; b) after performing said liner recess etching process, performing a fin recess etching process to remove a portion, but not all, of said at least one to-be-removed fin; and c) repeating steps (a) and (b) until the desired amount of said at least one to-be-removed fin is removed; and forming an insulating material in an area that includes an area formerly occupied by said at least one to-be-removed fin.
 15. The method of claim 14, further comprising performing at least one additional recess etching process to recess said layer of insulating material and to recess said liner layer such that a desired final fin height of the remaining plurality of initial fins are exposed above said recessed layer of insulating material and said recessed liner layer.
 16. The method of claim 14, wherein forming said liner layer adjacent said sidewalls of said initial fins comprises performing a conformal deposition process to deposit said liner layer adjacent said sidewalls of said initial fins and above a bottom of said trenches.
 17. The method of claim 14, wherein said liner layer is comprised of silicon nitride and said trench patterning hard mask layer is comprised of silicon nitride.
 18. The method of claim 14, wherein each of said etching processes set forth in step (b) consumes between 10-30 nm of a vertical height of said at least one to-be-removed fin.
 19. The method of claim 14, wherein, after performing step (a), an upper surface of said recessed liner layer is positioned at a level that is below a level of an upper surface of said at least one to-be-removed fin.
 20. The method of claim 14, wherein the etching steps performed in steps (a) and (b) are anisotropic etching processes. 